Magnetic detector.



No. 877,069. PATENTED JAN 21, 1908. L. DB FOREST.

MAGNETIC DETECTOR.

APPLICATION FILED NOV. 2, F903.

WITNESSES: {HIV-{N708 M Lee deFore-st. @WM a UNITED STATES PATENT OFFICE.

LEE DE FOREST, Ol NEW YORK, X. Y., ASSIGXOR TO GEORGE h. \YOODWOR'IU, O'l' BOSTON,

)IASSACH LSETTS.

MAGNETIC DETECTOR.

Specification of Letters Patent.

Patented Jan. 21, 1908.

Application filed November 2. 1903- Serial Iio. 179.443.

To (1 whom it may concern.

lle it known that 1., 11m; or. Fonnsr, a citizen ol' the l nit ed States, and resident of the city, county, and State of New York. have invented certain new and useful Improve-S ments in Magn tic Detectors, of which the 5 following is aspecification.

.\l v invention relates to an improvement in magnetic oscillation detectors for use i| wireless signaling, and comprises the. novel features which will hereinafter he described and particularly pointed out in the claims.

The object of my invention is to simplify and improve the construction of such devices and particularly to avoid the variation in the intensity of signals produced by magnetic detectors due to the variation in intensity of the rotating magnetic field which is employed in certain types.

The accouumnying sir-2'. ings represent in a more or less diagramrtatic manner constructions embodying fhc features of ,my inven tion.

F gure t represents a longitudinal sectional view of a porticn of th detector and the connection of the aerial circuit therewith. Fig. l is an end view of the same device showing the connection of both the aerial and signal receiving or translating circuits. Fig. 3 is a diagram illustrating the manner of connecting the various portions of the device in their respective circuitsj Fig. 4 is a view similar to Fig. 2 representing a ditl'erent method of connecting the translating circuit. Figs. 5 and 6 are respectively plan and eleval tion showing a modilied construction of the magnetic detector.-

The above drawings illustrate constructions embodying mvinveution in forms which are now preferred by me, said drawings being however of more or less diagrammatic character and therefore omitting details which are unnecessary to make clear the construction and operation intended.

In the operation of magnetic detectors employing a variable magnetic field, this field is most generally produced by the rotation of a permanent magnet, so that its oles move adjacent to an end of the core 0 the magnetic detector. With such devices, experience has proved that the intensity of the signal produced depends in a measure upon I the position of the poles of the magnet relative to the ends of the core. There is one position in each half revolution of the magnet in which the intensity of the signal is at aniii'iimum and other positions substantially 30 removed therefrom in which the intensity of the signal is at a maximum. the positions between these two pl")tlitcing' signals gradually varying from maximum to minimum. it has also been found that the intensity of the signal is greatest when the pole. of the magnet is approaching the core of the detector. One obj ct of my invention is to avoid this variation in the intensityo the signal produced, and to maintain the intensity of the signal constantly at a maxinuun. I secure this result by a eonstriu-tion of the detector, in which the core is divided up into a number of parts which are so distributed with relation to the magnet that when the cli'ect is at the maximum in one part it is at a minimum in.another.' the result being av maintenance of a substantially constant rate of variation in the magnetic lield as it atl'ects a l of these parts of the core. The result may I he said to be the production of a. magnetic field which is constantly varying at a uniform rate and yet in which the sum total of the magnetism in the detector as a whole remains substantially constant.

In the form of construction shown in Figs. 1. 2 and 3, I have divided the detector up into a plurality of parts each of which is substautially an independentdetector consisting of the cores t, the coils B through which pass the aerially induced waves, and the 1 coils i) which form a part of the translating circuit. These separate or individual detectors are grouped together in a ring, as viewed from an end or the position shown in Fig. 2, thus forming a substantially annular magnetizable me|uber. The manner of wiring the individual parts is clearly shown in Fig. 3, which does not correctly represent the relative position of these individual parts but represents whatmight be called the projection of these parts upon a plane, that; is, as they would be it rolled out or in the tint. This View is given in order to clearly show the manner of connecting the various parts or units of the detector. The coils B which immediately surround the cores C and through which the aerially induced waves are passed, are connected in series between the antenna A and the earth E. The signal coils D are similarly connected in series in the translating circuit. 'lhis-circuit is herein shown as provided with a telephone receiver T, although any form of translating device may be employed.

The individual parts or units of the detector may have their coils connected in series, as shown in Fig. 3, or by groups' in series parallel as desired. They might also nets F and F are employed, one at each end These two magnets of the detector cores. are mounted upon a common shaft G which coincides with the axis of the detector, passing through the opening lett at the center in the formation of the detector. This may be provided with means for rotating it of any desired character. The double magnet here in shown produces a strong magnetizable effect upon the detector, and is ellicicntin this way. It will be seen that when a magnet is rotated with its poles adjacent the ends of a detector of this construction, certain parts or units of the detector are all at times in favorable position for the production of a strong signal impulse, and no matter what the position of the magnet, some part of the detector is at all times in the position of maximum effect. There will therefore be no variation in the intensity of the signal produced due to the position of the ma-met, and one of the objections to the use of detectors of the magnetic ty e is thereby avoided.

Figs. 5 and 6 i lustrate a modified construction of magnetic detector within the scope of this invention. In this case the core 0' is m the form of a ring, and the coil B extends about this ring throughout its circumference, as does also the signal coil 1) which forms a part of the translating circuit. The magnet F" is mounted with its axis coincident with the axis of the ring, the poles N and S thereof preferably being formed, so as to embrace the ring. Vith this construction the location of the pole in the ring is constantly shifting, fol-owing the poles of the rotating magnet. The same effect as to the maintenance of a constantly changing magnetic effect which is uniform in amount and at the same time with the maintenance of the sum of the magnetic conditions in the detector as constant, is obtained. With this form of magnetic detector it is possible to rotate the magnet at any speed desired, as its rotation does not produce a click or signal in the telephone. The tendency of one part of the detector to produce a click is neutralized by $5 the tendency of another partto neutralize 1 this click. and consequently no sound is heard in the telephone receiver. 1 have found that such a device is very sensitive, and that there are no perceptible fluctuations in the strength of signals due to the position of the magnet or magnets in their revolution.

It is evident that the constructions herein illustrated and (lest ribcd may be widely varied without however departing from the spirit of my invention. 1 do not therefore wish to be limited to the exact constructions herein shown, but to claim the same broadly.

' Having thus described my invention what I claim is:

1. In a magnetic oscillation detector, the combination with magnetizable means consisting of a plurality of magnctizahle cores arranged annularly with respect to each other; of a magnet arranged substantially concentric with respect to said magnetizable means; said magnet and magnetizablc means being constructed and arranged to be relatively rotatable.

2. In a magnetic oscillation detector, the combination with magnetizable means con sisting of a plurality of magnetizable cores arranged annularly with respect to each other of means operable by received oscillations to vary the induced magnetization of said magnetizable means; and a magnet arranged substantially concentric with respect to said magnet-izable means; said magnet and magnetizable means being constructed and arranged to be relatively rotatable.

3. In a magnetic oscillation detector, the combination with a substantialy annular magnetizable member, of a magnet arranged concentric therewith, the annular member and magnet being constructed to be relatively ro atable.

4. A magnetic oscillation detector comprising a plurality of cores and coils thereon grouped about a common axis, and a magnet mounted to turn upon a coi'ncidentaxis.

5. A magnetic oscillation detector comprising a plurality of cores dis osed about a common axis, separate coils or said cores connected in series, and a magnet mounted to turn upon a coincident axis.

6. A magneti oscillation detector comprising a plurality '-f cores disposed about a common axis, sena'za e but connected coils for the cores, a magnet shaft coincident with said axis, and a mar-net at each end of the cores having its poles adjacent the ends of cores which are dianwt-rically disposed in the device.

In testimony whereof, I have hereunto afiixed my signature this 8th day of October 1903, in the presence of two witnesses.

LEE DE FOR EST.

Witnesses:

GEORGE W. Thomas, H. L. Sxrmin. 

